Fuel is delivered to the combustion chamber(s) of a gas turbine engine by one or more fuel injectors.
Fuel injectors for aircraft gas turbine engines are often mounted externally of a casing of the combustion chamber at respective apertures through the casing. Each injector has a mounting flange which is sealingly connected to the external surface of the casing with a feed arm and tip of the injector passing through the aperture and the tip engaging into the head of the combustion chamber. Bolts secure the flange via threads in the casing.
However, a problem with this arrangement is that the securing bolts are working against the casing internal pressure. More particularly, the pressure difference across the casing may be in the range from about 35 to 4100 kPa, with the high pressure within the casing forcing the injector flange away from the casing. This can cause air leakage, and hence engine efficiency loss. On the other hand, an advantage of the arrangement is that the injector can be removed on-wing for maintenance or replacement.
An alternative arrangement has the injector flange sealingly connected to the internal surface of the casing. This overcomes the air leakage problem because the sealing arrangement is working with the internal pressure, i.e. the pressure difference across the casing forces the flange toward the casing. However, the internally mounted injector cannot be easily removed as the flange is too large to be withdrawn through the aperture. Thus the injector can only be removed from the inside, which requires a major engine strip, rendering on-wing maintenance or replacement effectively impossible.